1. Field of the Invention
The present invention relates to touch panels and, particularly, to a carbon nanotube based touch panel and a display device using the same.
2. Discussion of Related Art
Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels at the front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing or touching the touch panel with a finger, a pen, stylus, or another like tool while visually observing the display device through the touch panel. Therefore, a demand exists for touch panels that provide superior visibility and reliable operation.
Up to the present time, different types of touch panels, including resistance, capacitance, infrared, and surface sound-wave types have been developed. Due to their higher accuracy and low-cost of production, resistance-type touch panels have been widely used.
A conventional resistance-type touch panel includes an upper substrate, a lower substrate, and a plurality of dot spacers. The upper substrate includes an optically transparent upper conductive layer formed on a lower surface thereof. The lower substrate includes an optically transparent lower conductive layer formed on an upper surface thereof, and two pairs of electrodes connected to the optically transparent lower conductive layer at four edges along the X and Y directions respectively. The plurality of dot spacers is formed between the optically transparent upper conductive layer and the optically transparent lower conductive layer. The upper substrate is a transparent and flexible film/plate. The lower substrate is a transparent and rigid plate made of glass. The optically transparent upper conductive layer and the optically transparent lower conductive layer are formed of conductive indium tin oxide (ITO). The two pairs of electrodes are formed by silver paste layers.
Voltages are separately applied by an electronic circuit to the two pairs of electrodes. In operation, an upper surface of the upper substrate is pressed with a finger, a pen or the like tool, and visual observation of a screen on the display device provided on a back side of the touch panel is allowed. This causes the upper substrate to be deformed, and the upper conductive layer thus comes in contact with the lower conductive layer at the position where pressing occurs. Voltages between the position where pressing occurs and the electrodes are changed. Thus, the deformed position can be detected by the electronic circuit.
However, the ITO layer (i.e., the optically transparent conductive layer) is generally formed by means of ion-beam sputtering, and the method is relatively complicated. Furthermore, the ITO layer has poor wearability/durability, low chemical endurance, and uneven resistance in an entire area of the panel. Additionally, the ITO layer has relatively low transparency in humid environments. All the above-mentioned problems of the ITO layer makes for a touch panel with relatively low sensitivity, accuracy, and brightness.
What is needed, therefore, is to provide a durable touch panel and a display device using the same with high sensitivity, accuracy, and brightness.